interface Point{
	x:number,
	y:number,
	z?:number
}
var p:Point;
p={
	x:12,
	y:5,
	z:11
}
interface A{
	a:number,
	b:number
}
interface B{
	a:number,
	b:number,
	c:number
}
var c:A|B;
console.log(c.c)//此时会报错